Pump systems



N. ERLAND AF KLEEN PUMP SYSTEMS Oct. 4, 1960 2,954,741

Filed Aug. 24, 1955 2 Sheets-Sheet l 2411. 3O W J 26 i .|o l8 28 iii 22M I R 3e FROM 20 l E Q RESERVOIR 32- u Tzg, Z

SEPARATOR FROM RESERVOIR lOu INVENTOR. NILS ERLAND AF KLEEN \wmwmATTORNEY Oct. 4, 1960 N. ERLAND AF KLEEN 2,954,741

PUMP SYSTEMS Filed Aug. 24, 1955 2 Sheets-Sheet 2 TO LOAD FROM RESERVOIR\A FROM 80 RESERVOIR A I 1 lOd l h.

\ n- F- n 1 ll l INVENTOR. n NlLS ERLAND AF KLEEN 7 BY 3 \(LQ 7 1 \wmuQ1 ATTORNEY PUMP SYSTEMS .Filed Aug. 24, 1955, Ser. No. 530,387

15 Claims. (Cl. 103-255) This invention relates to improvements in pumpsystems, and particularly to an improved system including aheat-actuated pump, referred to herein as a thermopump.

Briefly, a thermopump comprises a unit in which a liquid is heated toform vapor. This vapor is recurrently collected and condensed bycyclically reversing the relative rates of vaporization and condensationin the unit.

By connecting the unit to a fluid supply source and a delivery point orload through a pair of check valves, the fluid expansion and contractionaccompanying this cyclical action can be utilized to eifect a transferof liquid from the source to the load.

It is among the general objects of the present invention to provide animproved heat-actuated pumping system of relatively high efliciency.Ancillary objects of the inven tion include the provision of aheat-actuated system for pumping liquids against relatively high loadpressures, the provision of a compound pumping system making mostefficient use of a plurality of individual thermopump units, and theprovision of a system effectively utilizing either a plurality ofdifferent liquids or the same liquid under different operatingconditions.

In accordance with one feature of the invention, certain of theforegoing objects and advantages are attained in a system wherein athermopump is isolated from the principal liquid flow circuit,hereinafter called the load circuit, by a separating chamber, andwherein means are provided for dissipating stored heat which mightotherwise interfere with the pumping action. In accordance with afurther feature of the invention, the dissipating means may comprise asecond pump whichis arranged to operate on heat which has already doneuseful work in a first pump and which would otherwise be wasted. Inaccordance with another feature of the invention, two serially connectedthermopumps are operated in such fashion as to supply liquid atrelatively high pressure for any desired purpose,

atefnt O respect to the supply of heat thereto. In accordance with afurther feature of the invention, two pumps can be'op- 'erated inparallel with respect to the circulating effect thereof and in cascadewith respect to the supply of heat thereto.

A more complete understanding of the invention, and l of further objectsand features thereof, can be had from the following description ofillustrative embodiments pump and the pumps are connected in series tothe; load circuit, and

heating and condensing tubes.

Figure 4 is a schematic diagram of a compound thermo- I pump systemembodying the invention wherein the pumps are connected in parallel to aload circuit.

Referring to Figure 1 of the drawing, this figure shows a system forpumping one liquid by means of a thermopump 10 containing a differentliquid. For example, the pump unit 10 may be filled with water, and thepumping circuit 12 may contain some corrosive liquid such as an acid, analkali or the like. ,The pump itself is shown for illustrative purposesas being of the type disclosed in US. Patent 2,553,817, comprising anupright heating tube oi generator 14, heated by an electrical heatingelement 16. The upper end of the generator is provided with an invertedU-shaped bend 18. The bend 18 serves as a trap to accumulate vapor as itis formed in the heated portion of the generator. One end of the bendcommunicates with a U-shaped vapor tube 20 which is of considerablysmaller cross-section than the generator 14 in order to insure deliveryof vapor therethrough as a coherent body rather than as a series ofbubbles.

The vapor tube 20 extends downwardly from the generator and thenupwardly to the upper portion of an upright condensing tube or condenser22. The condenser 22 may be of substantially the same cross-sectionalsize as the'generator l4 and is adapted to hold a body of liquid whichis in communication with the liquid in the generator. The upper end ofthe condenser 22 is provided with an outlet tube 24 communicating with avalve assembly '26 which controls the discharge of liquid from and thedelivery of liquid to the pump unit.

' The valve assembly includes two check valves 28, 34). One valve, 30,permits only the discharge of liquid from the pump unit, while the othervalve, 255, permits only the entry of fresh liquid into the pump unit.

It will be noted that the valve assembly 26 maintains only a smallvolume of liquid between the two valves 28, 30. This arrangement appearsto contribute in some instances to the smooth operation of the pumpunit, since it makes it possible to draw relatively cool liquid into thetop of the condenser. Only a small amount of the previously dischargedwarm liquid remaining in the valve assembly will be drawn back into thecondenser, and this warm liquid is well cooled by admixture with therelatively large quantity of fresh liquid drawn into the unit.

Communication between the lower ends of the generator 14 and thecondenser 22 is effected by means of a reservoir 32 adapted to hold abody of the pump liquid in communication with the lower portions of boththe The reservoir 32 preferably is of such size as to hold a body ofliquid of suflicient mass to minimize heat transfer from the liquid inthe lower end of the generator to the liquid in the lower end of thecondenser. By thus minimizing the heat transfer from the heating tube tothe condensing tubeit is possible to prevent elevation of thetemperature of liquid in the upper portion of the condensing tube to anon-condensing value.

In the embodiment ofthe invention presently being described, the checkvalve assembly 26 is connected to a loop 34 which includes cooling meansin the form of tubing this 36 or the like. This loop 34 is connected bya separator element 40 to a valve assembly 42 in the load circuit 12. Itwill be understood that the pump ltl causes liquid to circulate throughthe load circuit 12. The circuit 12 may connect a reservoir and 'a loaddevice (not shown), or may comprise a closed loop through which liquidis continually recirculated by the pump 10.

In the Figure 1 system, the separator element 4%- prevents mixing of theliquids in the pump it andin load circuit'12.. Thus, the element 40 maycomprise a U tube 44 filled with mercury or some other liquid which willnot mix readily with either the-pump or load circuit liquids.

Of course, other comparable separating elements can be used. Forexample, as shown in Figure 2, the separator may comprise adiaphragm'assembly, comprising a housing 50enclosing a flexiblediaphragm 52 which divides the housing into two separate compartments54, 56. One compartment, 54, then would be coupled .to the loop 34 whilethe other compartment, 56, would communicate with the load circuit valveassembly 42.. Additional examples of separator elements are givenhereinafter.

In considering the operation of the system shown in Figure 1, it will beassumed that the pump unit is completely filled with a readilyvaporizable liquid, such as water. When heat is applied to the generator14 by passing current through the heating element 16, the liquid in thegenerator will boil, forming vapor. As the vapor is generated, it willcollect in the inverted U- shaped portion 18 of the generator. Thegeneration of vaporwithin the pump unit will force liquid out of theunit 10 through the outlet check valve 30. The

vapor will continue to form and to displace the liquid in the generatortube 14 until the vapor reaches the lowermost point of the vapor tube20. ,At this point, the liquid in the generator will be at the samelevel in the upright leg of the generator and in theivapor tube 20, andthe taller column of liquid in the condenser 22 will be supported by thepressure of the vapor in the generator. Once vapor starts upward in thevapor tube 20, the hydrostatic balance will be upset, and liquid willcontinue to cause the liquid to flow upwardly through i the generator.The resulting ingress of relatively cool liquid into the heating zonewill terminate further vaporization under these conditions and expeditethe condensation taking place in the upper portion of the con- .denser.Thus, once condensation is initiated it will conthe pump unit. Underthese conditions, liquid will flow into the pump through the check valve28, with the result that relatively cool liquid will flow into the upper.tinue rapidly and quickly establish a partial vacuum in Y portion ofthe condenser until the pressure within the pump unit returns to normal.At this point inthe operating cycle, the liquid again substantiallycompletely fills the pump unit and is at rest. The continued applicationof heat to the generator once again will establish vaporizing conditionstherein and the pump cycle will repeat. tinuously applied to thegenerator will cyclically discharge liquid from the pump unit underpressure and.

draw fresh liquid thereinto.

It will be seen, therefore, that heat con- It can be seen that continuedoperation of the pump involves the cyclical transfer of heat from thegenerator 14 to the condenser 22 in the form of latent heat contained inthe vapor flowing to the condenser. While the liquid in the condenserwill be replaced continuously by flow through the check valve assembly26, it

can be appreciated that the temperature of the cir'culating liquid inthe closed loop 34 will tend to increase due to the continued supply ofheat until eventually the liquid in the pump 10 and in the closedcircuit 34 might reach a temperature at which vapor would no longercondense rapidly, and the operation of the pump would stop. In order toprevent this from happening, the aircooled finned tube sections 36 areprovided in the closed loop circuit 34 in order that the heat comingover to the condenser can be dissipated as the liquid circulates throughthe closed circuit 34. a

The movement of liquid back and forth in the connection line 24 betweenthe condensing tube 22 and the check valve assembly 26 will beduplicated in the sep arating element 40, resulting in a correspondingliquid movement on the load circuit side of the separator. Thus, theliquid to be circulated will alternately be drawn in through the loadcircuit inlet check valve 43 and then forced out through the outletcheck valve 45 to obtain the desired circulation.

. In Figure 3, there is shown an alternative arrangement for operating apump system with different liquids in the load and pumping circuits,together with a modified arrangement for-extracting heat from a pump oondenser in order to prevent overheating thereof. In this case, additionalefliciency also is obtained, because the heat that is simply dissipatedby the finned tubing sections 36 in the Figure 1 system is utilized inFigure 3 to operate a second pump feeding the same load circuit.

Referring to Figure 3, a first thermopump 10a is connected to a checkvalve assembly 42a in a load circuit 12 bya separator 40. The pump 10adiffers from the pump 10 of Figure 1 in that the generator 14a isconnected directly to the condenser 22a rather than being connectedthrough a reservoir. The condenser 22a opens into a tank 23 above thecondenser, and the tarfli 23 is alsoconnected back to the condenser by abranch tube 25. While the reason is not clearly-understood, it has beenfound that this arrangement of parts gives better efliciency under someconditions than the pump configuration 10 of Figure 1, particularlywhere it is desired to operate pumps in series with respect to heatflow, as will be explained presently.

In the pump 10a, hot liquid tends to flow. to the top of the tank 23 onthe vaporizing cycle, while cooler liquid returns to the pump on thesuction stroke through the branch tube 25.

Beyond the check valve assembly. 42a, a surge or accumulator tank 58 isconnected to the load circuit 12 to absorb the fluctuations in liquiddelivery which will occur due to the cyclical operation of the pump 10a,permitting the pump 10a to operate at a pressure which .is lower thanthat imposed by the load. The accumu- 'lator 58 may alternativelycomprise a flexible walled tank similar to the diaphragm chamber 50 ofFigure 2 or the. bellows of Figure 5. Downstream from the accumulator 58inthe load circuit 12 is a second check valve assembly 42b, throughwhich liquid is circulated by a second thermopump 10b.

The second thermopump 10balso is shown in somewhatdifierent form thanthe first pump 10a, although it is to be understood that the varioustypes of pumps shown in the drawings are interchangeable.

The second pump 1% has. a condenser 22b, a vapor tube 20b and. agenerator 14b, generally similar to the corresponding parts 22a, 20a,14a of the pump 10a. Howeveryan additional element 62 is provided in thesecond pump 10b for vapor collection. The vapor collector 62 comprisesanelongated cylinder of substantially greater cross-section than thegenerator tube 14b. The generator tube 14b opens into the top'of thevapor collector 62,'while the vapor tube 20b slopes downwardly from apoint on the upperperiphery of the collector. The condenser 22b isconnected to the collector 62 at or near the lower end thereof, while asmall diameter inlet tube 64 connects the bottom of the generator 14bwith the collector 62 at a point partway up the collector. V H p w Thecollector 62 preferably contains afloat element 66 which separates theliquid from the vapor phases as vapor is delivered from the generator tothe vapor collector.

. In the Figure system, thefirstpump 10a will be filled with aliquidhaving a substantially higher boiling point than the liquid beingcirculated through the load the sameliquid as that being circulatedthrough the load circuit. Since this second liquid has a lower boilingpoint than the liquid filling the first pump a, it is possible tooperate the second pump 10b on the heat which is passed into the firstpump condenser 22a with the incoming vapor. In this way, the condenserof the first pump can be cooled without a special and separate coolingcircuit as in Figure 1, and at the same time the efliciency of thesystem as a whole wil be increased by using heat which would otherwisebe dissipated to operate the second pump. Accordingly, the generator 14bof the second pump is placed in heat exchange relation with the firstpump condenser 22a; preferably being disposed inside the condenser tank23 as shown. Fins 36 may be placed on the generator 14b to increase theheat transfer surface.

Whenthe temperature of the liquid in the condenser tank 23 comes up tothe boiling point of the liquid in the second pump 10b, the liquid inthe generator 14b will be heated to the boiling. point and willvaporize. The vapor thus formed will collect in the top of the generator14b and also in the collecting chamber 62, and in so doing will forceliquid from the generator 14b and collector 62 and through the outletvalve 45b, the principal flow of liquid being down through the collector62 and up through the condenser 22b. Vapor will also collect in thevapor tube 2%. Once the vapor in the tube b reaches the lowermost pointin the tube and starts uptoward the condenser 22b, the hydrostaticbalance in the system will be upset. The head of liquid in the condenser2211 now will force liquid to flow upwardly in the collector 62 andgenerator 14b. In turn, this will force the vapor out of the collector62 and through the vapor tube 20b. Meanwhile, the vapor forced throughthe tube 20b will condense as it is discharged into the relatively coolcondenser 22b. The hydrostatic refilling of the collector 62 willproceed very rapidly, once initiated, so that the vapor in the collectorwill all be delivered quite abruptly to the condenser 22b, where it cancondense very quickly if the condenser temperature is low enough. Theresulting pressure drop in the system will cause a fresh charge ofliquid to be drawn in through the inlet valve 43b to replace thecondensed vapor.

The float 66 greatly reduces the area of contact between the liquid andthe vapor in the collector 62, and presents to the vapor a'stablesurface that needs to be heated only once rather than a changing,turbulent liquid surface that will continuously condense some vapor andthereby reduce the pumping efliciency.

In, order to have the smallest possible area of liquidvapor contact, thefloat, 66 is preferably shaped to conform rather closely incross-section to the inside crosssection of the collector 62, and withcross-sectional dimensions just enough smaller than the correspondinginside dimensions of the vessel 62 to allow free float movement.

The foregoing and other advantageous features of the pump 10b aredescribed in detail and claimed in the copending application of R. E.Coleman, Serial No. 297,371, filed July 5, 1952, now Patent No.2,744,470,

and assigned to the assignee of the present invention.

It can be seen, then, that the first pump 10a will deliver liquid to theaccumulator 58 at some preselected pressure, and the second pump willdeliver liquid to the. load at a higher pressure.

In a typical case, for example, the problem might be to use heat from asource at a temperature of the order of 750 F., to pump water against aload pressure of, say 70 p.s.i.g. While it would be possible to operatea single pump with water across the temperature range, at 750 F. theentire system would have to be able to withstand pressures far in excessof the 70 pound load pressure. Instead, using an arrangement as in 6Figure 3, the first pump might be filled with mercury and designed foroperation across a temperature range of, say 750 F. (maximum generatortemperature) to 350 F. (average condenser temperature) and a pressurerange of 30 to 15 p.s.i.a. In this case, of course, the separator 40 maycomprise a U-tube like the tube 44 of Figure 1, since the mercury in thepump 10a would not mix with the water in the load circuit 12b.

The second pump would then operate with the load circuit liquid (water)across the temperature and pressure ranges of, say, 310 F. (maximumgenerator temperature) to F. (average condenser temperature) and 70 to30 p.s.i.a., respectively. This assumes a temperature drop of 40 ,F.through the walls of the generator 14b.

In the present illustrative example, it is assumed that l a moderaterise in temperature of the load circuit liquid is permissible.Accordingly, the load circuit 12 is coupled to the condenser 22b of thesecond pump by a short coupling line 24b so that fresh load circuitliquid will circulate in and out of the condenser 22b on each cycle tokeep this condenser cool. If this is not permissible, the volume of thecoupling line 24b can be made substantially greater than the volume ofone stroke of the pump 10b so that the same liquid, rather than freshliquid, will circulate in and out of the pump condenser 22b. In suchcase, the coupling line 24b should be provided with fins or othercooling means to prevent overheating of the condenser. Alternatively, acooling circuit arrangement can be used such as the circuit 34 as shownin Figure 1, but with the separator 40 eliminated.

It can be seen that the downstream check valve 45b in the second checkvalve assembly can only be opened by a pressure of 70 lbs. absolute inthe check valve assembly 42b. Hence, the accumulator 58 is necessarybetween the two sets of check valves 42a, 42b to absorb the output ofthe first pump 10a at a lower pressure than that imposed on the systemby the load. On its suction stroke, the second'pump 10b will draw inliquid from the accumulator and will pass it on to the load at thehigher pressure as required.

The principle of operating a second pump on the reiected heat from afirst pump can be applied in a number of other ways to obtain highsystem efiiciency. For example, additional pumps for circulatingdifferent liquids in separate circuits can be coupled to each other asillustrated by pump 10e in Figure 3 to make efiicient use of availableheat.

Another way in which thermopumps can be used advantageously in seriesrelation with respect to heat flow, is to connect them in parallel to acommon load circuit. This is shown in Figure 4, where two check valveassemblies 42c, 42d are connected in a common load ci-rcuit 12 byparallel lines 72, 74. A first coupling line 240 extends from one checkvalve assembly 42c to the condenser 220 of a first thermopump 10cthrough a separator 40. A second coupling line 24d extends from theother check valve assembly 42d to the condenser 22d of a secondthermopump 10d.

The generator 14c of the first pump 1% is arranged to receive heat fromany suitable source, shown for simplicity as an electrical heatingelement 16. The generator 14d of the second pump 10d is placed insidethe first pump condenser 220 to operate on the rejected heat of thefirst pump. The two pumps 10c, 10d shown in Figure 4 are of the samegeneral type as the pump 10 in Figure 1, the principal difference beingthat the reservoirs 32c, 32d for cutting down transfer of heat areoriented vertically rather than horizontally to make the overallassembly more compact.

In the system shown in Figure 4, it can be assumed for one example thattwo liquids with diiferent boiling points are usedv in the two pumps, asin the Figure 3 system. 'In this case, the liquid in the second pump 10dis the '7 same as that in the loadcircuit 12, while thQ'liqllid'lll thefirst pump 100- is a higher boiling point liquid, as previouslydiscussed. In this case, however; the two pumps will operate across thesame pressurediflerential.

ing element at 40 separating the first 100 from the load circuit 12.While a variety of such pressurereducing elements are well known per se,there is illustrated in Figure one suitable type, comprising a housing'80 containing a bellows element 82 and provided with a spring '84partially balancing.

Using Water as the liquid forthe entire system, for example, the firstpump c might operate at generator and condenser temperatures of 400- F.and 309 F., respectively, across a corresponding range of pressurescompressing the bellows for pressure -from 250 p.s.i.a. -to 68 p.s.i.a.The second pump 10d would then operate, say, at generatorand-condensertemperatures of 250 F. and 160 F., across-a pressure range from-30p.s.i.a. to p.s.i,a. 'The pressure stepdown ratio of the bellows element80 would beof the order of 8 to 1 and 4 to 1 at the two pressureextremes.

It will be seen that a compound pumping system feeding a load circuit inseries fashion, somewhat-similar to the arrangement shown in Figure 3,and using the same liquid in both pumps, can .be madeby using a pressurereducing device as in Figure 5. In other Words, two pumps can beoperated in series for circulating liquid through a load circuit, andusing the same liquid in both pumps, with the heat in the condenser ofone pump furnishing the energy to operate the secondpump in the same waythatit does in thesystem of Figure 3.

This is illustrated in Figure 6, wherein the condenser 22 of a firstpump 10 is connected directly to one check valve assembly 42 by acoupling line 240i volume greater than that of one stroke of the pump,While a second pump 1% is connected to a second set of check valves 42bthrough a separator 40 comprising a step-up device. With thisarrangement, the first pump 10 must operate against a higher pressurethan the second pump 10b, which means that the boiling point of theliquid in. the first pump will be substantially above" the boiling pointof the same liquid in'the second pump, The pressure translating element40 between the second pump condenser 22b and the check valves 42b isrequired because,

as a practical matter,there will be some gap between the averagetemperature in the first pump condenser 2-2 and that inside thegenerator 14b of the second pump. Accordingly, there will also be a gapbetween the minimum pressure for the first pump and the maximum pressuregenerated by the secondpump. This gap is covered by the pressure step-upelement 40,: which converts the volume changes in the second pump tosimilar changes at a higher pressure level in the load circuit 12. Thebeneficial features of this arrangement on the efliciency of the systemas a whole are'related to the pressure-volume-temperaturecharacteristics of the pump liquid, as well as to the series heattransfer'arrangernent. By reference to standard steam tables, theefiiciency of the thermopump, operating with Water, can be computed atdifierent pressures in accordance with the formula max min) X steamwater) steam"- water) X718. where'P is the maximum-pressure within thepump, in pounds .per sq. ft.; P is the minimum pressure within t We P n1161" t; V e are 191W? "8 of the fluid, lll'Cll-"fll'. per pound; Histhe enthalpy of thefiuid inB.t.u. per pound.

Such a computation shows'thatothe pump will operate most efficientlywith a pressure ri seoacrossthe pump of about 450 p.s-.i.a. If itistattemptedlto operate .a single pump at any greater pressure rise,the. applied heat will not be utilized at. maximum efiiciency.vFurthermore, regardless of the efficiency (i.e.,pressure"rise) at whichthe pump is operated, the heat passing over'to thecondenser will bewasted. i l I 1 W o {1 In the Figure 6 system, therefore,'.'a higherefiiciency can be obtained for a given temperature range (say, 800 F.),because the first pump canbe operated across its most efiicient range atthe level of, say, 8745 p.s.i.g.- to 445 p.s.i.g., while the second pumpalso is operating .across its 400 pound maximum efiiciency rangebetween, say, 400 p.s.i.g. and 0. The gap in pressure between the upperlimit of 400 psig. for the second'pumpoand the lower limitof 445 for thefirst pumpflwill betakencare of by the pressure reducing element 40betweenothe first pump and the load circuit. -Thus, maxirnuin efiiciencywill be maintained across the entire available temperature range.

What is claimed is: 1 1. In a heat-actuated pumping system forcirculating liquid through a load circuit,.first and secondliquid-filled pump units within which to vaporize and condense liquid toforce liquid .to flow out of and vinto,said units, a coupling lineconnecting said first unit to said load circuit, a first pair of checkvalvesin said load circuit located one upstream and one downstream ofsaid coupling line through which to pass'liquid from said load circuitinto and out of said coupling line, a ,second coupling line connectingsaid second unit to said load, circuit, a second pair of check valves insaid load circuit located one upstream and one downstream of said secondcoupling line through which to pass liquid to and from said load circuitthrough said, second coupling line, and means in one of said couplinglines'separatingthe liquid in that one of said pump units which isconnected to said one coupling line from theliquid in said load circuit.

- 2. The invention defined in claim 1, wherein said pairs of checkvalves are in series in saidloadcircuit. 3. The inventiondefined inclaim 1, wherein said load circuit includes two branches which aregconnected .in parallel between common portionsupstrearn and downstreamof said branches, said pairs of check valves being located one pair ineach of said branches.

4. In a heat actuated pumping system, in combination, a first pump unitand comprising a generatorwithin which to, vaporize said liquid, byheating, a condenser within which to condense vaporby cooling and meansconnecting said generator and said condenser to conduct comprising avgenerator withinwhich. to vaporize said liquid by heating, a condenserwithin which to condense vapor by cooling and means connectingsaidgenerator and said condenser to conduct liquid andvaporltherebetween, coolingmeans for said condenser oisaidfirst pumpunit, said cooling meanscomprising a structure in heat exchange relationwith said condenser and adaptedto be .filled with liquid, and a secondpumppnitcomprising a generator within whic tow ot z i s 2 l land. acondenserwithin whichto condenseyapor by cooling, .said cooling meansfor said; condenser .of said ,fir st zpump unitconstituting saidgenerator of said second pump unit, a circuit through which to circulateliquid, a first pair of check valves in said circuit, coupling meansconnecting one of said pump units to a point in said circuit betweensaid check valves, a second pair of check valves in said circuit, andcoupling means connecting the other of said pump units to a point insaid circuit between said second pair of check valves.

6. In a heatactuated pumping system, a pair of liquidfilled pump unitseach comprising: a generator within which to vaporize liquid by heating,a condenser within which to condense vapor by contact with a cool bodyof liquid in said condenser, and means connecting said generator andsaid condenser through which to transfer vapor and liquid therebetween;said generator of one of said units being in heat exchange relation withsaid condenser of the other of said units to provide heating for saidone unit generator and cooling for said other unit condenser; said unitsbeing charged with liquid at predetermined pressures; the boiling pointof the liquid in said one unit being lower than the boiling point of theliquid in said other unit at said predetermined pressures.

7. In a heat actuated pumping system, in combination, first and secondpump units each comprising a generator Within which to vaporize liquid,a condenser within which to condense vapor formed in said generator, andconduit means connecting said generator and said condenser through whichto transfer liquid and vapor therebetween, the generator of said secondpump unit being disposed within the condenser of said first pump unit toreceive heat therefrom.

8. The invention defined in claim 7 wherein said pump units are filledwith the same liquid, the liquid in said first unit being maintained ata higher pressure than the liquid in said second unit.

9. The invention defined in claim 7 wherein said units are filled withliquids which boil at different temperatures, said first unit beingfilled with a liquid which boils at a higher temperature than the liquidin said second unit.

10. In a heat actuated pumping system, in combination, first and secondpump units each comprising a generator within which to vaporize liquid,a condenser within which to condense vapor formed in said generator, andconduit means connecting said generator and said condenser through whichto transfer liquid and vapor therebetween, the generator of said secondpump unit being disposed within the condenser of said first pump unit toreceive heat therefrom, a circuit through which to circulate liquid, afirst pair of check valves in said circuit, conduit means connecting oneof said pump units to a point in said circuit between said check valves,a second pair of check valves in said circuit, conduit means connectingthe other of said pump units to a point in said circuit between saidsecond pair of check valves, and liquid separating means included withsaid last-named conduit means to prevent mixing of the liquid in saidcircuit with the liquid in said other pump unit.

11. The invention defined in claim 10 wherein said separating meanscomprises a pressure translating device through which to transfer liquidmovement at different pressure levels.

12. The invention defined in claim 10 wherein said pairs of check valvesare in series in said load circuit.

13. The invention defined in claim 10 wherein said 7 pairs of checkvalves are connected in separate parallel branches of said load circuit.

14. In a heat-actuated pumping system, the combination including a firstpump comprising a first vapor generator having a liquid therein andmeans to vaporize said liquid, a condenser having liquid therein, firstconduit means connecting said generator with said condenser foralternate cyclical flow of vapor generated in said generator to saidcondenser for condensation therein and release of heat and thereafterflow of liquid from said condenser to said generator whereby vapor iscyclically forced by pressure into and condensed in said condenser andthereafter liquid is directed into said generator from said condenser,second conduit means having means at one end preventing flow in onedirection and means at the opposite end preventing flow in said onedirection, a liquid'reservoir connected to said one end of said secondconduit to supply liquid to said conduit, third conduit means connectingsaid condenser to said second conduit means intermediate the endsthereof whereby liquid flowing in from said reservoir enters saidcondenser and liquid forced out of said condenser by the vapor pressureduring vaporization in said generator is delivered through said secondconduit and out said opposite end thereof; a second pump including asecond vapor generator having liquid therein, and means connecting saidsecond generator and said first pump for utilizing the heat released bythe latter for vaporizing liquid in the former.

15. In a heat-actuated pumping system, the combination including a firstpump comprising a first vapor generator having a liquid therein andmeans to vaporize said liquid, a condenser having liquid therein, firstconduit means connecting said generator with said condenser foralternate cyclical flow of vapor generated in said generator to saidcondenser for condensation therein and release of heat and thereafterflow of liquid from said condenser to said generator whereby vapor iscyclically forced by pressure into and condensed in said condenser andthereafter liquid is directed into said generator from said condenser,second conduit means having means at one end preventing flow in onedirection and means at the opposite end preventing flow in said onedirection, a liquid reservoir connected to said one end of said secondconduit to supply liquid to said conduit, third conduit means connectingsaid condenser to said second conduit means intermediate the endsthereof whereby liquid flowing in from said reservoir enters saidcondenser and liquid forced out of said condenser by the vapor pressureduring vaporization in said generator is delivered through said secondconduit and out said opposite end thereof; a second pump including asecond vapor generator having liquid therein, means connecting saidsecond generator and said first condenser for utilizing the heatreleased by the latter for vaporizing liquid in the former, and means insaid system for separating the liquid in one of said pumps from the restof said system.

References Cited in the file of this patent UNITED STATES PATENTS1,848,226 Scott-Snell et a1. Mar. 8, 1932 2,553,817 Erland af Kleen May22, 1951 2,688,923 Bonaventura et a1. Sept. 14, 1954 2,744,470 ColemanMay 8, 1956

